Gas foil bearings can be used for various machine types to support shafts rotating at high speeds. A preferred application of the gas foil bearings according to embodiments of the invention are radial bearings for a compressor rotating preferably at speeds between 10000 and 50000 RPM.
In this field of technology, several bearings types are known, for example oil lubricated radial ball bearings, oil lubricated journal bearings, active magnetic bearings and gas foil bearings. Embodiments of the invention deal with the latter. The gas foil bearing comprises normally a thin smooth radially inner surface layer and a bump foil radially outer surface layer, which allows for damping and thermal growth, centrifugal growth and compensation of miss-alignment of the shaft especially during high speed operation. Conventional gas foil bearings often can not cope with unbalance and misalignment resulting in excessive rotor vibrations. This can be a major problem for an especially radial gas foil bearing applied to a rotor of a compressor comprising an impeller with heavy aerodynamic load imposing additional dynamic forces to the gas foil bearings.
A gas foil bearing of the incipiently mentioned type for a centrifugal turbo blower is known from the patent applications US 2005/0163407A1, U.S. Pat. No. 4,208,076 A1, U.S. Pat. No. 4,274,683 A1, U.S. Pat. No. 4,296,976 A1, U.S. Pat. No. 6,158,893 A1. Except for the first previously mentioned patent applications, each document proposes to weld the foils to the carrier element. The first document proposes to insert one foil end respectively into a groove extending axially on the radial inner surface of the carrier element. While this solution to weld one foil end to the carrier element has the disadvantages of welding being a further manufacturing step and altering the material properties of the foils as a heat treatment, the known non-welding method to fix the foils to the carrier element as proposes in the first patent application mentioned has safety disadvantages. The conventional non-welding method goes along with the risk that the insertion of the foils into the groove is not sufficiently strong to avoid the foils getting loose. To avoid loosening of the foils further complex key-solutions must be provided which in most cases do not satisfy a requirement to a radial fixation or is complicated and expensive to manufacture.
The U.S. Pat. No. 4,295,689A1 shows a foil bearing comprising one metal sheet only which works for very small unit. The proposed design doesn't allow the fixation of more foils.